import pandas as pd
index = ['0','1','2','3','4']
columns = ['year','month','day']
dict = {'year':[2019,2020,None,2020,2022],'month':[3,None,6,9,12],'day':[4,2,21,2,15]}
df1 = pd.DataFrame(dict,index)
print('事件信息表:\n',df1)
df1['year']= [2019,2020,2021,2020,2022]
df1['month']= [3,9,6,9,12]
print('修改后:\n',df1)
